Zero Turn Radius Electric Riding Lawn Mower

40586 Views 50 Replies 15 Participants Last post by bennettdan, May 19, 2011

TheRedBaron

Discussion Starter · Jan 31, 2011

Hey everyone:

I am looking at doing a zero turn radius riding mower conversion. However, as been mentioned in other posts, a hydrostatic transmission is inefficient when used with an electric motor. My idea is to use two hub motors, one for each drive tire, instead. Then I would use another electric motor for the operation of the blades.

This is 3 electric motors however, which adds a degree of complication to the design.

So my main question is if that is too complicated a set up?
Comments, Questions, and Concerns are more than welcome!

(basic mower stats: 16hp mower briggs and straton engine, 48" deck, zero turn steering)

1 - 20 of 51 Posts

Woodsmith

· #2 · Jan 31, 2011

I guess it would be no more complicated then an electric wheel chair. A scrap donor chair may even provide you with a low power starting off point to learn from.
The cutter deck motor would only need an on off switch/contactor with a sepex or shunt motor.

major

· #3 · Jan 31, 2011

Woodsmith said:
I guess it would be no more complicated then an electric wheel chair. A scrap donor chair may even provide you with a low power starting off point to learn from.
The cutter deck motor would only need an on off switch/contactor with a sepex or shunt motor.

Hey Woody,

How about that sub forum for unusual vehicles, like karts, tractors, mowers, flying saucers, etc. Any progress?

Hey TheRed,

I usually don't like hub motors, but they may actually fit this application, go figure. Unless you live in a real hilly area or have towing requirements, the mower propulsion is relatively low power compared to the blade drive. So independent wheel motors might work, a couple kW apiece. You'll likely have problems finding ones which fit as most are designed for scooters.

But for the blade drive, you'll need a good size motor. That 16hp gas burner was sending most of its power to the blade. You might get by with a 6.6 inch diameter electric motor, but a 7.2 wouldn't hurt.

Kool project.

major

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TheRedBaron

Discussion Starter · #4 · Jan 31, 2011 (Edited)

Okay that makes sense! However, my greatest concern would be the independent wheel control. I would like to only have to buy one controller for both hub motors. However, I would have to have different power levels at times to each motor. Are there controllers that can accomplish this?

Oh and I am looking at using a brushless DC hub motors for the wheels.
An example of such a motor: http://www.hnmotors.de/product_info.php?language=en&products_id=42

Edit: From what I understand, you are not supposed tow with a zero turn radius lawn mower, however...I would like to plan on towing around at least 150-200lbs.

Woodsmith

· #5 · Jan 31, 2011

major said:
Hey Woody,

How about that sub forum for unusual vehicles, like karts, tractors, mowers, flying saucers, etc. Any progress?

major

We'd need to be looking at maybe a couple hundred threads in it to justify it and someone will have to find all the existing threads to populate it.

Us ordinary admin can't set it up but if we can show good justification then the forum owner can set it up to be populated.

Ziggythewiz

· #6 · Feb 1, 2011

I've been wanting to do this for some time.

I've seen a number of builds that use electric wheelchairs as a starting point, as most of the controls are already there. The cutting blade really doesn't need to be that powerful, I have an electric mower (22") and it pulls around 10 amps (120V AC) so a big blade should only need around 50 amps. I can't imagine using an EV size motor for just the blade, but if you go with an 11" you should be ready for the zombie apocalypse.

Here's a few examples I've come across, I think these all have gas blades, but that'd be the easiest part of the project.

http://members.iinet.net.au/~tnpshow/RCLM/intro.htm

http://rediculouslygoodlooking.com/

http://www.instructables.com/id/Arduino-RC-Lawnmower/

TheRedBaron

Discussion Starter · #7 · Feb 1, 2011

major said:
Hey Woody,

How about that sub forum for unusual vehicles, like karts, tractors, mowers, flying saucers, etc. Any progress?

major

First, an electric flying saucer would rock, but I'm unsure of the power requirements of such a thing. You perhaps would be better off w/ a fusion power plant instead of batteries but who knows?

Anyways, back to a less interesting project (we had wanted to do an electric ultralight but $$ is an issue there, I guess that is like a flying saucer).

The motor I have posted above I want to use as propulsion not for the blades; though hub motors may work for them too, hooked up to a simple switch. With a zero turn lawn mower, each handle would be hooked up to a hub motor and would allow independent operation.

Ziggythewiz, I don't know what your power rating on your blade mower was but I was looking at 1kw motors for the blades.

Also, anyone work with lithium batteries on an application like this or are the lead acids still the primary option here?

JRP3

· #8 · Feb 2, 2011

I don't know the actual efficiency losses of the hydrostatic setup but it certainly would be a lot easier and cheaper to use it than multiple motors and controllers. Efficiency losses could possibly be made up by just using an extra battery. Lithium would be neat but probably not cost effective.
Regarding creating another forum for unusual vehicles, I don't think there is enough demand, even though I own one myself. The occasional oddball can hang out here in All Conversions and not feel like an outcast

TheRedBaron

Discussion Starter · #9 · Feb 2, 2011

JRP3 said:
I don't know the actual efficiency losses of the hydrostatic setup but it certainly would be a lot easier and cheaper to use it than multiple motors and controllers. Efficiency losses could possibly be made up by just using an extra battery. Lithium would be neat but probably not cost effective.

Tried following your link but it appears to be broken

. Anyway, the stuff I found on hydrostatics seemed to indicate to me that their inefficiency was sufficiently high (especially something in the lawn mowing range) to really start hampering an electric motor-hydrostatic transmission coupling.

I am also interested in the maintenance issue. With brushless electric motors, there would be few issues in that department. The system would also be more straightforward (battery->controller->motor->wheels) instead of (battery->controller->motor->transmission->wheels).

Plus transmissions take up space-> space I could use to add more batteries to the mower perhaps?

PhantomPholly

· #10 · Feb 2, 2011

One good approach to any problem is to put each piece of the puzzle into perspective.

In the first post, the concern raised about using the hydrostatic drive is that it is inefficient.

Let's assume that it is only 50% efficient (Eee gads!). What percentage of your total power consumption does that represent?

Well, if out of 16hp 90% was going to the blades (likely true, if not more - 1.6 hp is an awful lot just to move you around at 4mph!), then 50% of 10% = 5% total power wastage.

Weigh that against the challenges of developing independent reversible controllers for independent wheel motors (now 3 motors).

For the extra weight and complexity of the extra motors and controllers, I think I'd just put on an extra battery.

If it ain't broke, don't fix it!

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Jimdear2

· #11 · Feb 2, 2011

Red Baron,

In light of the information on powerloss that PhantomPholly just posted and thinking of all of the problems you will see with a designed from scratch system.

Take a look at this item in Surplus Center.

https://www.surpluscenter.com/item.asp?item=13-1473&catname=powerTrans

All you need to add are wheels, frame, bateries, controller and a motor. Something that will turn those two pulleys at a constant speed up to 3000 rpm. I would run an independent deck motor, in fact I would have two packs 1 for the deck and 1 for the tractor.

I built an electric conversion Cub Cadet and am in process of converting one of those tow behind mower decks to electric.

I really did look at building a zero steer but I just couldn't find a tractor with a blown motor that I could afford back then.

Jim

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JRP3

· #12 · Feb 2, 2011

TheRedBaron said:
Tried following your link but it appears to be broken .

Wasn't actually my link, just some automated feature of the forum that creates links for certain terms. Annoying.

I am also interested in the maintenance issue. With brushless electric motors, there would be few issues in that department. The system would also be more straightforward (battery->controller->motor->wheels) instead of (battery->controller->motor->transmission->wheels).

Actually you'll need two controllers since you'll be sending different signals to each motor when turning if you don't use a transmission. Maintenance on brushed motors would not be a real issue in normal service.

Plus transmissions take up space-> space I could use to add more batteries to the mower perhaps?

True. You really need to figure out how much run time you need and how much battery it's going to take.

jeremyjs

· #13 · Feb 2, 2011

If it were me I'd just get a bigger permanent magnet dc or shunt motor and use a contactor to turn it on. I doubt you'd loose much power through the hydrostatic drive simply because you need very little of the power to drive the wheels; unless you're plowing snow with it or something.

If you go the direct drive route you need a minimum of 2 reverseable drive motors and a controller, throttle, gear reduction drive, etc on each and 1 large blade motor. The cost of that is going to add up fast and then you still have to deal with getting everything calibrated to work well and buy your batteries. If you simply go with 1 larger motor of a type that needs no controller you can put your extra money in the batteries and end up spending a lot less.

gor

· #14 · Feb 2, 2011 (Edited)

4

inefficiency?

efficiency of eaton hydraulic and AC55 ev motors:

i agree with Phantom and JR: all should be put in perspective:
efficiency of hydraulic drivetrain itself can be high (50hp hydraulic motor you can hold in your hand) - all the matter of fortune spend on design and components:
homeowner ztr cost $2-3k, industrial -$12-15,000;
ztr pump -$600; skid-steer pump-$6000
yes, 28hp lawnmower - engine, 4 wheels, seat, 2 pumps, wheelmotors and blades cost same as small car... : )))) and it eats fuel a day more than car in a week... (~10 gal)... OEMs going bigger and bigger, more heavier duty
highly efficient or not - obviously something should be done ...

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Ziggythewiz

· #15 · Feb 2, 2011

I've also considered mounting a blade under my bug, but someone made the gate a foot too small to get to the back yard...

TheRedBaron

Discussion Starter · #16 · Feb 8, 2011

Thanks everyone for the information! The mower I have found to convert is a Dixon ZTR 4423.

42'' deck with 3 blades
no hydraulics
fiberglass body
Briggs & Stratton 16hp Engine
Chain drive

So hub motors for the wheels are probably out. Probably end up doing the single motor design. However, I am still thinking of doing 3 independent motors for the blades. Not only does that eliminate belt wear and tear, the overall efficiency of the system should go up as well. Also the system wouldn't need a really complicated controller.

On top of all that, it would make cleaning/removing the deck/changing the blades much simpler. The motors could be mounted to the deck. Add universal connectors to the wiring and that only leaves the mechanical structure to worry about.

Thoughts?

Side Note: anyone know what the torque of a lawnmower blade should be around? The rpm's should be around 3000 but the torque would vary depending on the motor used.

Side Note II: Though with the hub motors, while design maybe more challenging, since the power needed to the wheels is fairly small, the motors and controllers for that kind of set up would be much smaller hence less expensive.

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TheRedBaron

Discussion Starter · #17 · Feb 8, 2011

Also, let me apologize to anyone who spent a lot of time looking into the issue of the hydrostatic drive efficiency. I was initially under the impression that the mower I was converting was a hydrostatic drive.

However, since I plan on performing more of these conversions, I probably will work on a mower with a hydrostatic drive so the information is still very much appreciated!

Plus other people get to use it as well!

ruckus

· #18 · Feb 8, 2011

Regardless of mower type, single moter is a good way to go for several reasons:

1. SIMPLE. 1 motor, 1 controller, 1 set of wires.
2. Hydrostat provides some back-pressure to help prevent runaway of series wound motors. With belt mower, this is more of a concern. Obviously, shunt wound is the ultimate solution here.
3. cost. one big motor is cheaper than multiple small/medium motors. Plus the cost of wiring and connectors etc etc..

I am glad you are doing this project. I have been DYING to do a mower conversion as our place eats gas mowers for lunch and the noise and pollution is horrible.

Can you post pics?

Please, please PLEASE can the powers that be create a mower/tractor/farm machinery conversion category in the forum???

Tractors have special issues that do not apply to cars such as the engine block acting as the frame.

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major

· #19 · Feb 8, 2011

TheRedBaron said:
However, I am still thinking of doing 3 independent motors for the blades.

Here's a deck I did a while back

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ruckus

· #20 · Feb 9, 2011

awww. Talk about JEALOUS.

There seem to have been no Electraks sold in MT.

(at least I have never seen one)

Will you give us some specs? Series or shunt wound? Controller or hard-wired? If series, do you have to limit speed or do the blades provide enough limiting force?

Thanks

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